A striking new image from the James Webb Space Telescope shows a rare object called an Einstein ring. This shows what appears to be a ring-shaped object in the sky, but is actually created by two separate galaxies and the epic forces of gravity.
There’s a useful astronomical phenomenon called gravitational lensing, in which a large object like a galaxy or a cluster of galaxies has so much mass that it actually bends spacetime. If a massive object sits in front of a more distant object, as seen from Earth, the massive object can act like a magnifying glass, letting us see the very distant object in more detail than would normally be possible. This is a relatively common finding in astronomical images, and is one way that scientists are able to study extremely distant galaxies.
Most often, these lensed objects appear curved or distorted by the gravitational forces acting on spacetime. But occasionally, the objects line up in such a way that the distant object appears as an almost perfect circle: this is then called an Einstein ring.
“When the lensed object and the lensing object line up just so, the result is the distinctive Einstein ring shape, which appears as a full circle (as seen here) or a partial circle of light around the lensing object, depending on the precision of the alignment,” Webb scientists explain. “Objects like these are the ideal laboratory in which to research galaxies too faint and distant to otherwise see.”
The galaxy which is close to us and is seen the center of this image is an elliptical galaxy (meaning it is smooth with a bright core) that is part of a cluster called SMACSJ0028.2-7537, while the more distant background galaxy that is stretched into the ring shape is a spiral galaxy (like our Milky Way). Even though this galaxy has been tugged into what looks like a circle shape, you can still see the hints of its spiral arms at the top and bottom of the image.
The image was created using data from both James Webb’s NIRCam instrument and also the Hubble Space Telescope’s Wide Field Camera 3 and the Advanced Camera for Surveys instruments, showing how effective these two telescopes can be when they work together.
